Occupational (Physical) Exposures and Male Infertility

In document ALPHA PARTICLES DEPOSITION AND ITS EFFECTS ON LUNGS, MALE INFERTILITY AND (halaman 46-50)

ABSTRACT

2.1 Introduction

2.2.3 Occupational (Physical) Exposures and Male Infertility

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houses of people who smoke may have high radon levels and their risk of lung cancer is especially high (EPA 1992, Mendez 1998).

EPA 2009 and 2010 recommended that with today’s technology, radon levels in most homes could be reduced to 2 pCi/l (0.02WL=74Bq/m3) or below. Thus, it considered an optimum of indoor radon between 2 and 4 pCi/l. In fact, the emanation rate of radon gas has been found to vary from month to month, season to season and year to year, depending on the geological formation, ventilation rate, building material, rate of porosity, soil permeability, etc. (Garakani et al. 1988, Hubbard and Hagberg 1996, Gillmore et al. 2005, Ismail and Hussyin 2007, Prasad et al. 2009, Bochicchio et al. 2009, Groves-Kirkby et al. 2010, Binesh et al. 2011). As a result, long-term measurements of the radon gas are suitable.

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In addition, most of this exposure comes from radon in the air (1300 µSv) (Sankaranarayana1999).

The point of importance in the context of this study is that the mutations induced by radiation of human germ cells will cause an increase in the frequency of the genetic material of the spermatozoa, in an increase in sterility, which can be identified by their respective phenotypes. Thus, human fertility is reduced due to pollution, which may be caused by gene mutation, lowered sperm counts, impairment of sperm motility, or many other reasons. Neither the average mutation rate nor the numbers of loci capable of mutating to dominant detrimental form, as well as mutations that cause sterility are known (Sutton 1975).

Review of the effects of radiation resulting in infertility began from study on the effects of ionizing radiation causing genetic damage in human cells. Numerous occupational exposures have been linked to impairment of male fertility (Sheiner et al.

2003). However, studies have been limited by inadequate sample sizes, inappropriate study designs, and/or selection bias. Additionally, the use of semen measures as surrogates for male fertility has been problematic, because there is considerable intra individual variability, substantial overlap between infertile men and fertile men, and poor correlation between fertility and decrements in semen measures.

Salvin (1956) submitted a report on his research under the title ‘Effect of Atomic Radiation on the Incidence of Sterility and Mutation.’ He carried out his research after the atomic bombings in Hiroshima and Nagasaki, with the cooperation of the United States Atomic Energy Commission. This committee supplied funds to the Atomic Bomb Casualty Commission, which sponsored investigations of the results of the bombings.

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However, owing to the following reasons, he could not obtain satisfactory results: no accurate birthrates were maintained by the Japanese authorities before the bombings took place, and it was difficult to ascertain the damage to fertility by the bombs alone, because during the war, there were other factors affecting fertility, such as fear, anxiety, and malnutrition.

1. There was the great difficulty in obtaining statistics in Japan with reference to the incidence of sterility and mutation rates related to atomic bombing.

2. There was no apparent increase in the incidence of sterility as determined by the birth rates in bombed and unbombed cities.

3. The sterility dose of radiation was approximately the same as the lethal dose of whole body radiation.

4. The fertility of men who survived the bombings returned, as a rule, after several months.

5. The number of stillbirths and abnormalities was greatly increased as the result of atomic radiation of pregnant women. Most of the abnormalities were microcephalics, which is consistent with the current known effects of X-rays on fetus in uterus.

6. There has been no appreciable effect till date on the mutation rate due to the bombings. However, the great majority of geneticists feel that there is an analogy between the mutations produced in animals and humans by radiations, and that the effects of radiation will ultimately express themselves. They also feel that we must balance the patient well at the concealed illness, and use radiation only when one would seem to outweigh the other. There can be nothing but the genetic disadvantage for man in artificially raising his mutation rate above that which sufficed for his evolution till

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date. The effects of atomic radiation are destructive by increasing the incidence of sterility temporarily.

In 1959, Oakberg submitted his experiment about irradiation of mouse by the doses of 20 rads of gamma rays and 100, 300, and 600 rad of X-rays. He concluded that the killing of cells, rather than inhibition of mitosis, was the primary factor responsible for radiation-induced depletion of spermatogonia.

In 1960, Heller and Rowley investigated some excellent cell data available with regard to the men testes. They studied the radiation effects on human spermatogenesis in biopsies and ejaculates from a group of 67 volunteers administered with testicular doses of 8-600 rad of X-rays. They found that the spermatogonia in the mouse were most radiosensitive cells for doses under 50 rad (Rowley et al. 1974, Gaulden 1983).

In 1971, Léonard submitted his research entitled “Radiation induced translocations in spermatogonia of mice.” He found that the many years of radiation translocation would cause heritable semi-sterility.

In 1974 Rowley et al., carried out made an experiment on uniform irradiation of the human testes. A portable unit was developed to provide uniform irradiation of the human testes. The device had built-in radiological protection and provided a dosage independent of the subject geometry, uniform to within ±5%. Single doses, between 8 and 600 rad were administered to the testes of human subjects. Dose-response relationships and recovery times were determined for each dose range studied. In 1975 Sutton (1975) found that mutations will cause sterility.

In 1979, Evans et al, explained that the nuclear radiation in nuclear dockyard had induced aberrations of the chromosome of the worker. In 1986, Germai submitted his

In document ALPHA PARTICLES DEPOSITION AND ITS EFFECTS ON LUNGS, MALE INFERTILITY AND (halaman 46-50)